Removal and/or melting of snow and ice on roadways, bridges, sidewalks and the like is a major task in many areas.
Various chemicals have been used to assist in the removal and/or melting of snow and ice. Conventional road salt, has been used extensively in part due to its melting ability and also its relatively low cost. However, it has been found that the low cost of salt has been offset in part by the damage to roadways, bridges, underground cables (such as telephone or electrical cables) and the like, not to mention automobiles, caused by its use. Salt's corrosivity has led to damage to pavement and to the steel structure of bridges and surrounding structures. Moreover, the accumulation in run-off water has caused problems with vegetation. Accumulation in ground water has caused health problems with drinking water due to increased sodium contents. Other salts, such as calcium chloride, have been used; however, calcium chloride too has similar problems and causes accumulation of chloride ion in the environment, which is undesirable.
Accordingly, there has been extensive study on alternative deicing chemicals which are noncorrosive, environmentally acceptable and which are economically practical.
The Federal Highway Administration sponsored an extensive study by the Bjorksten Research Laboratory (BRL) on deicing chemicals. The study's report "Alternative Highway Deicing Chemicals" published March, 1980, identified calcium magnesium acetate (CMA) as a leading candidate for replacing road salt. Since the publication of the BRL report, various groups and individuals have been working on the preparation and testing of deicing agents comprising calcium magnesium acetate, calcium acetate and/or magnesium acetate. (See, e.g., U.S. Pat. Nos. 4,426,308, 4,444,672, 4,511,485, and 4,606,836.) However, preparing CMA economically on a commercial scale has been a problem. See, e.g., Ganoy, Alan B., "Preparation of High Quality Calcium Magnesium Acetate Using a Pilot Plant Process", Federal Highway Administration (January, 1986). Dried large lumps of CMA in the product has been a problem, as has unacceptable levels of fugitive dust from product. See, e.g., "Continuous Production Calcium Magnesium Acetate/Sand Deicer" prepared by Cedarapids Inc. for Iowa Highway Research Board, June 3, 1985.
Previous processes have exhibited problems with dusting of powdered lime and unacceptable levels of acid odor and vapor in recycled material, bed material, and even product.
Previous calcium magnesium acetate-coated sand deicing agents have used a wetting agent, such as a cement-grinding aid, as a binder. See U.S. Pat. No. 4,588,512 to Rippie.
U.S. Pat. No. 4,699,725 to Gancy discloses magnesium calcium acetate compositions and processes for their manufacture.
Our copending U.S. patent application Ser. No. 003,097, filed Jan. 14, 1987, discloses deicing compositions comprising alkaline earth or alkali metal carboxylates and processes for their production. The disclosure of U.S. Ser. No. 003,097 is incorporated herein by reference.
Our copending, commonly assigned, U.S. Pat. application Ser. No. 77,148, filed July 24, 1987, discloses deicing compositions comprising calcium magnesium acetate double salt. The disclosure of U.S. Ser. No. 77,148 is incorporated herein by reference.